Method for producing high-purity organoiridium compounds

ABSTRACT

The present invention relates to a process for preparing highly pure tris-ortho-metallated organoiridium compounds and such pure organometallic compounds which may find use as coloring components in the near future as functional components (=functional materials) in a series of different types of applications which can be classed within the electronics industry in the widest sense.

Organometallic compounds, especially compounds of the d⁸ metals, willfind use as coloring components in the near future as active components(=functional materials) in a series of different types of applicationwhich can be classed within the electronics industry in the widestsense.

The organic electroluminescent devices based on organic components (fora general description of the construction, see U.S. Pat. No. 4,539,507and U.S. Pat. No. 5,151,629) and their individual components, theorganic light-emitting diodes (OLEDs) as well as polymericlight-emitting diodes (PLEDs), have already been introduced onto themarket, as shown by the available car radios having organic displaysfrom Pioneer or a razor from Philips with a PLED display. Furtherproducts of this type will shortly be introduced. In spite of all ofthis, distinct improvements are still necessary here for these displaysto provide real competition to the currently market-leading liquidcrystal displays (LCDs) or to overtake them.

A development in this direction which has emerged in recent years is theuse of organometallic complexes which exhibit phosphorescence instead offluorescence [M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson,S. R. Forrest, Applied. Physics Letters, 1999, 75, 4-6].

For theoretical reasons relating to spin probability, up to four timesthe energy efficiency and power efficiency are possible usingorganometallic compounds. Whether this new development will establishitself depends strongly upon whether corresponding device compositionscan be found which can also utilize these advantages (tripletemission=phosphorescence compared to single emission=fluorescence) inOLEDs. The essential conditions for practical use here are in particulara long operative lifetime, a high stability against thermal stress and alow use and operating voltage, in order to enable mobile applications.Secondly, there has to be efficient chemical access to the correspondinghighly pure organoiridium compounds. Especially taking into account thescarcity of iridium, this is of crucial importance for theresource-protective exploitation of the compound class specified.

In the literature, several processes have been described for thepreparation of tris-ortho-metalated organoiridium compounds. The generalaccess routes, the yields achieved by them and their disadvantages willbe laid out briefly hereinbelow using the basic skeleton of the compoundclass mentioned, fac-tris[2-(2-pyridinyl)-κN)phenyl-κC]iridium(III).

Starting from hydrated iridium(III) chloride and 2-phenylpyridine,fac-tris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) was obtained in anabout 10% yield after a complicated chromatographic purification process[K. A. King, P. J. Spellane, R. J. Watts, J. Am. Chem. Soc., 1985, 107,1431-1432].

K. Dedeian et al. describe a process starting from iridium(III)tris(acetylacetonate) and 2-phenylpyridine, by whichfac-tris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) was obtained in 45%yield. Analogously to the above-described process, it is necessary inthis process too to free the product of impurities by chromatographicprocesses, and in this case, required by the solubility behavior,halogenated hydrocarbons are used [K. Dedeian, P. I. Djurovich, F. O.Garces, G. Carlson, R. J. Watts, Inorg. Chem., 1991, 30, 1685-1687].

In a third known process,di-μ-chlorotetrakis[2-(2-pyridinyl-κN)phenyl-κC]diiridium(III), whichinitially has to be prepared in an approx. 72% yield from hydratediridium(III) chloride and 2-phenylpyridine [S. Spouse, K. A. King, P. J.Spellane, R. J. Watts, J. Am. Chem. Soc., 1984, 106, 6647], is used as areactant. This is then reacted with 2-phenylpyridine and double molaramounts of silver trifluoromethanesulfonate based on thedi-μ-chlorotetrakis[2-(2-pyridinyl)-κN]phenyl-κC]di-iridium(III)compound. After chromatographic purification, the authors obtaintris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) in 75% yield [M. G.Colombo, T. C. Brunold, T. Riedener, H. U. Gudel, Inorg. Chem., 1994,33, 545-550]. In addition to the chromatographic purification which isagain effected with the aid of halogenated hydrocarbons, the use ofdouble molar amounts of silver trifluoromethanesulfonate based on thedi-μ-chlorotetrakis[2-(2-pyridinyl-κN)phenyl-κC]di-iridium(III) isdisadvantageous, one reason being that silver traces can barely beremoved from the product.

The best process to date was described by P. Stössel et al. in WO02/060910. This process, consisting of the reaction of iridium(III)tris(acetylacetonate) or of a similar 1,3-diketo chelate complex with acorresponding pyridine-aryl or -heteroaryl compound in the presence of adipolar protic solvent with vigorous heating for a prolonged period (>20h), gives very good yields (up to 96%) and likewise very good purities(>99.9%).

The description in this disclosure is very good; in repeat experiments,it was also possible to reproduce the appropriate results; however, itwas noticeable that the synthesis in some cases did not function as welland under some circumstances no longer functioned at all at irregularintervals or in the case of other ligands. The cause of this was unclearfor some time.

In the Table 1 below, these literature data are compared for a betteroverview, including the comparative experiment carried out in Example 1.TABLE 1 Literature comparison of known preparation processes Reference 2Reference 1 Literature Comp. Ex. Reference 3 Reference 4 Reactants IrCl₃Ir(acac)₃ Ir(acac)₃ [Ir(ppy)₂Cl]₂ Ir(acac)₃ 2-phenylpyridine2-phenylpyridine 2-phenylpyridine 2-phenylpyridine 2-phenylpyridineAgO₃SCF₃ Solvents 2-ethoxy- ethylene ethylene none ethylene ethanol/glycol glycol glycol water Temperature — 196°-198° C. 196°-198° C. 110°C. reflux Concentration 0.03 mol/l 0.02 mol/l 0.02 mol/l — 0.1 mol/l ofiridium reactant Molar ratio 1:4 1:6.3 1:6.3 1:15 1:10 of iridiumreactants to 2-phenylpyridine Reaction time 24 h 10 h 10 h 24 h 60 hYield approx. 45% 39.3-44.0% 75% 92-96% 10% as a by- product of[Ir(μ-Cl) (ppy)]₂ Purity by no data no data 94.0-96.0% no data >99.9%HPLCReference 1: K. A. King, P. J. Spellane, R. J. Watts, J. Am. Chem. Soc.,1985, 107, 1431-1432. S. Spouse, K. A. King, P. J. Spellane, R. J.Watts, J. Am. Chem. Soc., 1984, 106, 6647-6653.Reference 2: K. Dedeian, P. I. Djurovich, F. O. Garces, G. Carlson, R.J. Watts Inorg. Chem., 1991, 30, 1685-1687.Reference 3: M. G. Colombo, T. C. Brunold, T. Riedener, H. U. GüdelInorg. Chem., 1994, 33, 545-550.Reference 4: P. Stössel et al., WO 02/060910.

From this overview, it can be seen easily that the process according toreference 4 is distinctly superior to the other known processes.However, the above-outlined problem of poor yield and of the occasionaloccurrence of irreproducibility and problems when other ligands are usedarise.

It has now been found that, surprisingly, a process, as described below,starting from IR complexes or mixtures of such complexes or mixturescomprising such IR complexes which do have acetylacetonate or diketonateligands but do not have the high symmetry of iridium(III)tris(acetylacetonate), has distinctly better yields and shorter reactiontimes than the process according to reference 4. Moreover, this inparticular allowed the “inexplicable” reproducibility problems outlinedto be eliminated and impressively increase the yields for further ligandsystems.

The present invention provides a process for preparing homolepticIr(III) complexes of the formula (I)

in which:

-   CyD is a cyclic group which contains at least one donor atom,    preferably nitrogen or phosphorus, via which the cyclic group is    bonded to the metal and which may in turn bear one or more    substituents R; the CyD and CyC groups are joined together via a    covalent bond;-   CyC is a cyclic group which contains a carbon atom via which the    cyclic group is bonded to the metal and which may in turn bear one    or more substituents R;-   R is the same or different at each instance and is H, F, Cl, Br, I,    NO₂, CN, a straight-chain, branched or cyclic alkyl or alkoxy group    having from 1 to 20 carbon atoms, in which one or more nonadjacent    CH₂ groups may be replaced by —O—, —S—, —NR¹—, —CONR², —CO—O—,    —CR¹═CR¹— or —C≡C—, and in which one or more hydrogen atoms may be    replaced by F, or an aryl, aryloxy, arylamine or heteroaryl group    which has from 4 to 14 carbon atoms and may be substituted by one or    more nonaromatic R radicals; where a plurality of substituents R,    both on the same ring and on the two different rings, together may    in turn form a further mono- or polycyclic, aliphatic or aromatic    ring system;-   R¹ and R² are the same or different at each instance and are H or an    aliphatic or aromatic-hydrocarbon radical having from 1 to 20 carbon    atoms,    characterized by the reaction of an iridium(III)-containing reactant    which contains at least one diketonate structural unit of the    formula (II)    in which:-   R⁴, R⁶ are the same or different at each instance and are a linear,    branched or cyclic alkyl group having 1-20 carbon atoms, in which    one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,    —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or more    hydrogen atoms may be replaced by F or aromatic groups each having    from 3 to 14 carbon atoms, or an aryl and/or heteroaryl group having    3-20 carbon atoms or an alkoxy group OR¹,-   R⁵ is the same or different at each instance and is a linear, cyclic    or branched alkyl group having 1-20 carbon atoms, in which one or    more nonadjacent CH₂ groups may be replaced by —O—, —S—, —NR¹—,    —CONR²—, —CO—O—, —CR¹≡CR¹— or —C≡C—, and in which one or more    hydrogen atoms may be replaced by F or aromatic groups each having    from 3 to 14 carbon atoms, or an aryl and/or heteroaryl group having    3-20 carbon atoms,-   R¹ and R² are the same or different at each instance and are H or an    aliphatic or aromatic hydrocarbon radical having from 1 to 20 carbon    atoms,    excluding homoleptic diketonate complexes of the formula (II) and    compounds of the formula (II) which contain two ligands of the    formula (III)    where the CyC and CyD radicals in formula (III) are each as defined    under formula (I), with a compound of the formula (IV)    in which the CyD and CyC radicals are each as defined under formula    (I).

The diketone formed in the reaction is removed by means of known methodsand the target compound is isolated.

A homoleptic complex is understood to mean a complex in which only thesame type of ligands are bonded to a metal. The opposite would be aheteroleptic complex in which different ligands are bonded to a metal.

The process according to the invention is illustrated by scheme 1.

Preferred inventive iridium(III)-containing reactants of the formula(II) are characterized in that they contain a structure of the formula(V)

where R⁴, R⁵ and R⁶ are each as defined under formula (II) and theiridium metal is hexacoordinated by the four oxygen atoms of thediketonate ligands and two monodentate ligands which may either beanionic (X) or uncharged (Y); n may be 0, 1 or 2. The complex isnegatively charged (m=1−) when n equals 2, the complex is uncharged(m=0) when n=1, and positively charged (m=1+) when n=0. The monodentateX and Y ligands may be cis or trans relative to one another.

Preferred inventive iridium(III)-containing reactants contain a compoundof the formula (V) in which X is the same or different at each instanceand is a fluoride, chloride, bromide or iodide anion.

Particularly preferred iridium(III)-containing reactants contain acompound of the formula (XI)

where R⁴, R⁵ and R⁶ are each as defined under formula (II), X is thesame or different at each instance and is a Cl, Br or I anion, and E isan alkali metal cation, ammonium or phosphonium ion. The monodentate Xligands may be cis or trans relative to one another.

Preference is likewise given to iridium(III)-containing reactants whichcontain a structure of the formula (VI)

where R⁴, R⁵, R⁶ are each as defined under formula (II) and where Z, asa bidentate and/or bridging ligand, is bonded to the iridium in achelating manner and is either an uncharged ligand Z⁰, for examplebipyridine, phenanthroline, ethylenediamine, propylenediamine, or 2-, 3-or 4-aminopyridine, or a monoanionic bidentate ligand Z¹, for examplediketonate, carboxylate, picolinate, aminocarboxylate or 1-ketoalkoxide,or a dianionic bidentate ligand Z²/for example oxalate, malonate,phthalate, isophthalate, terephthalate, oxide or peroxide. m is 1+ whenZ=Z⁰, 0 when Z=Z¹, and 1− when Z=Z².

Preference is further given to inventive iridium(III)-containingreactants which contain structures of the formula (VII)

where R⁴, R⁵ and R⁶ are each as defined under formula (II) and theligand Z, instead of being bonded in a chelating manner as in formula(VI), is bonded in a bridging manner, so that a plurality of iridiummetal atoms which are coordinated simultaneously by two diketonateligands are bonded to form oligomer-like (o≧2) and polymer-likestructures (o to 100 000). G is the same or different at each instanceand is either a monovalent anion X or an uncharged monodentate ligand Y.n and p are the same or different at each instance and are 0 or 1.Depending on the selection between uncharged, monoanionic and dianionic,bidentate and/or bridging ligands Z, and also between uncharged andmonoanionic, monodentate ligands as end groups G, the resultingstructures are multiply positively or negatively charged or uncharged.

Preference is likewise given to inventive iridium(III)-containingreactants which contain structures of the formula (VIII)

in which R⁴, R⁵ and R⁶ are each as defined under formula (II) and theligand Z which is bidentate and/or bonded in a bridging manner and maybe uncharged (Z⁰), monoanionic (Z¹) or dianionic (Z²) joins two iridiummetal atoms which are already coordinated by two diketonate ligandsbonded in a chelating manner and may each also be bonded to amonodentate uncharged or anionic ligand (G). n and p are the same ordifferent at each instance and are 0 or 1.

Suitable selection of the ligands Z and G gives rise to structures ofthe formula (VIII) which may be singly or doubly negatively charged(m=1− or 2−), or else singly or doubly positively charged (m=1+ or 2+),or uncharged (m=0). The bridging ligand Z and the monodentate ligand Gmay be bonded cis or trans relative to one another on the iridium metal.

Preference is further given to inventive iridium(III)-containingreactants which contain structures of the formula (IX)

where R⁴, R⁵ and R⁶ are each as defined under formula (II) and theligands Z may be bonded in a bridging manner over two iridium metalatoms. Depending on the selection of Z, the iridium-containing reactantsmay be doubly negatively charged (m=2−) up to doubly positively charged(m=2+). Single charges or uncharged iridium-containing reactants arelikewise possible. The iridium is additionally coordinated by fouroxygen atoms of the diketonate ligands.

Particular preference is given to iridium(III)-containing reactantswhich contain structures of the formula (VI), (VII), (VIII) or (IX),characterized in that the uncharged bidentate and/or bridging ligands Z⁰are the same or different at each instance and are bipyridine,phenanthroline, ethylenediamine, propylenediamine, or 2-, 3- or4-aminopyridine.

Particular preference is likewise given to iridium(III)-containingreactants which contain structures of the formula (VI), (VII), (VIII) or(IX) characterized in that the monoanionic bidentate and/or bridgingligands Z¹ are the same or different at each instance and areacetylacetonate, carboxylate, for example formate, acetate orpropionate, picolinate, aminocarboxylate, for example 2-aminoacetate or3-aminopropionate, 1-ketoalkoxides, for example tropolonate, benzoin,azide, cyanate, isocyanate, thiocyanate, isothiocyanate, halides, forexample chloride, bromide and iodide.

Particular preference is likewise given to iridium(III)-containingreactants which contain structures of the formula (VI), (VII), (VIII) or(IX) in which the dianionic bidentate and/or bridging ligands Z² areoxalate, malonate, phthalate, isophthalate, terephthalate, oxide orperoxide.

In addition, preference is likewise given to iridium(III)-containingreactants which contain structures of the formula (X)

where R⁴, R⁵ and R⁶ are each as defined under formula (II) and Q is amonoanionic monodentate ligand X or a β-diketonate which is bonded tothe metal via the carbon atom between the two keto carbon atoms.

Particular preference is given to iridium (III)-containing reactantswhich contain structures of the formula (X) where Q is a fluoride,chloride, bromide or iodide ion.

Particular preference is given to iridium (III)-containing reactantswhich contain structures of the formula (V), (VII), (VIII) and/or (IX)and in which X is the same or different at each instance and is amonovalent anion such as OH⁻, F⁻, Cl⁻, Br⁻, I⁻, SCN⁻, CN⁻, SH⁻, SeH⁻, N₃⁻ alkoxide, nitrate, carboxylate of the formula R¹COO⁻,cyclopentadienide (C₅H₅ ⁻) or hydride (H⁻).

Particular preference is likewise given to iridium(III)-containingreactants which contain structures of the formula (V), (VII) and/or(VIII) and in which Y is the same or different at each instance and isan uncharged monodentate ligand such as H₂O, H₂S, a dialkyl sulfide ofthe formula (R¹)₂S, a dialkyl sulfoxide (R¹)₂SO, NH₃, a primary,secondary or tertiary amine, an alcohol of the formula R¹OH, an ether ofthe formula (R¹)₂O, a thiol of the formula R¹SH, pyridine, quinoline, anitrile of the formula R¹CN, CO, a phosphine of the formula P(R¹)₃, aphosphine oxide of the formula OP(R¹)₃, an arsine of the formula As(R¹)₃or a phosphite of the formula P(OR¹)₃.

Inventive iridium(III)-containing reactants are likewise mixtures of atleast 2 iridium(III)-containing reactants which contain structures ofthe formula (II), or (V) to (XI).

The synthesis method illustrated here allows iridium(III) complexes ofthe formula (I) including the iridium(III)-containing reactants (1) to(12) depicted by way of example below to be prepared.

Inventive reaction media are high-boiling dipolar-protic solvents suchas ethylene glycol or propylene glycol, or else higher diols orpolyalcohols, for example glycerol, or else polyether alcohols such aspolyethylene glycols, for example PEG600 and PEG1000, and also theiretherified analogs, for example triethylene glycol dimethyl ether orpoly(ethylene glycol) dimethyl ether, and also NMP.

According to the invention, the reaction is carried out within atemperature range of from 100° C. to 250° C. According to the invention,the concentration of the iridium(III)-containing reactant is in therange from 0.05 to 1.00 molar.

The inventive molar ratio of the iridium(III)-containing reactant to theligand of the formula (IV) is from 1:4 to 1:20; preference is given to aratio of from 1:6 to 1:15; particular preference is given to a ratio offrom 1:8 to 1:12.

The preferred concentration of the reactant of the formula (IV) is inthe range from 0.50 to 10.00 molar, more preferably in the range from0.80 to 2.50 molar.

According to the invention, the reaction is carried out within from 20to 120 h, preferably in the range from 30 to 60 h. A reaction time lessthan that specified can have the consequence of incomplete conversion ofthe iridium(III)-containing reactant used, which can lead to yieldlosses and to contamination of the product with iridium(III)-containingreactant or intermediates.

As can be taken from the examples, some of the compounds of the formula(I) are obtainable via a process according to the prior art only in verymoderate yields and purities. The process according to the invention insome cases actually opens up the route to iridium(III) complexes of theformula (I).

This invention therefore further provides homoleptic Ir(III) complexesof the formula (I)

in which CyD, CyC, R, R¹ and R² are each as defined under formula (I),characterized in that they have been obtained by the above-describedprocess.

The compounds obtained by this process have over the compounds accordingto the prior art that they have greater purity, preferably greater than99%, more preferably greater than 99.5% (by NMR or HPLC), and are thusbetter suited to electronic appliances.

The present invention is illustrated in detail by the examples whichfollow without any intention to restrict it to the examples. It is thuspossible for those skilled in the art in the field of organic synthesis,without any further inventive activity, to carry out the inventivereactions on further systems as described above.

EXAMPLES Synthesis of tris-ortho-metallated organoiridium compounds

The syntheses which follow were carried out up to the workup under a drypure nitrogen atmosphere or pure argon atmosphere using carefully driedsolvents. The reactants used were purchased from Aldrich (ethyleneglycol), ABCR (Na[Ir(acac)₂Cl₂]) and Heräus (iridium(III)acetylacetonate).

The ligands 1-phenylisoquinoline, 2-phenylpyridine,2-benzothiophen-2-ylpyridine were prepared by literature methods bySuzuki coupling from the corresponding boronic acids and 2-bromopyridineor 1-chloroisoquinoline.

The syntheses are compiled in Table 2, Examples 1, 3 and 5 beingcomparative examples according to the prior art, and Examples 2, 4 and 6being inventive examples. TABLE 2 Ir content Iridium(III) - Ex- (%containing ample Ligand*** by wt.) reactant Yield Purity 1*  ppy 39.29Ir(acac)₃ 65.2-67.5%   >98% 2*  ppy 39.69 Na[Ir(acac)₂Cl₂]90.1-93.6% >99.9% 3** piq 39.29 Ir(acac)₃ 40.3-42.8% >99.0% 4** piq39.69 Na[Ir(acac)₂Cl₂] 87.9-91.7% >99.8% 5** btp 39.29 Ir(acac)₃52.3-55.4% >37.4% 6** btp 39.69 Na[Ir(acac)₂Cl₂] 86.9-89.7% >99.1%*40 h at 200° C., shorter reaction time than described in WO 02/060910**40 h at 180° C.***ppy (2-phenylpyridine), btp (2-benzothiophen-2-ylpyridine), piq(1-phenylisoquinoline)

Example 1 (Comparative Example)fac-tris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III)

(according to: P. Stössel et al., WO 02/060910)

4.90 g (10.0 mmol) of iridium(III) acetylacetonate and 15.52 g (14.3 ml,100 mmol) of 2-phenylpyridine were added to 100 ml of degassed ethyleneglycol. The suspension was heated under reflux (oil bath temperature200-210° C.) with good stirring for 40 h. After cooling to roomtemperature, a mixture of 240 ml of ethanol and 60 ml of aqueous 1Nhydrochloric acid was poured with stirring into the reaction mixturewhich contained the fac-tris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III)product in the form of a yellow, finely crystalline precipitate. Afterstirring for 5 minutes, the precipitate was filtered off with suctionthrough a glass suction filter (P3); the yellow, finely crystallineprecipitate was washed three times with 30 ml of a mixture of ethanoland aqueous 1N hydrochloric acid (4:1, v:v), five times with 30 ml of amixture of ethanol and water (1:1, v:v) and five times with 30 ml ofethanol, and subsequently dried under high vacuum at 80° C. for 5 h andat 200° C. for 2 h. The yield, at a purity of >98% by NMR, was 4.27-4.42g, corresponding to 65.2-67.5%.

¹H NMR (CDCl₃): [ppm]=7.84 (m, 3H), 7.58 (m, 6H), 7.48 (m, 3H), 6.82 (m,6H), 6.69 (m, 6H).

Example 2 (Inventive) fac-tris[2-(2-pyridinyl-κN)phenyl-κC]iridium(III)

Procedure analogous to Example 1, except that iridium(III)acetylacetonate was replaced by 4.84 g of Na[Ir(acac)₂Cl₂] (Ir content39.69%) (10.0 mmol).

The yield, at a purity of >99.9% by HPLC, was 5.90-6.13 g, correspondingto 90.1-93.6%.

¹H NMR (CDCl₃): [ppm]=see Example 1.

Example 3 (Comparative Example)fac-tris[2-(2-isoquinolinyl-κN)phenyl-κC]iridium(III)

4.90 g (10.0 mmol) of iridium(III) acetylacetonate and 20.53 g (100mmol) of 1-phenylisoquinoline were added to 100 ml of degassed ethyleneglycol. The suspension was heated under reflux (oil bath temperature180° C.) with good stirring for 40 h. After cooling to room temperature,a mixture of 240 ml of ethanol and 60 ml of aqueous 1N hydrochloric acidwas poured with stirring into the reaction mixture which contained thefac-tris [2-(2-isoquinolinyl-κN)phenyl-κC]iridium(III) product in theform of a red, finely crystalline precipitate. After stirring for 5minutes, the crystals were filtered off through a glass suction filter(P3); the red, finely crystalline precipitate was washed three timeswith 30 ml of a mixture of ethanol and aqueous 1N hydrochloric acid(4:1, v:v), five times with 30 ml of a mixture of ethanol and water(1:1, v:v) and five times with 30 ml of ethanol, and subsequently driedunder high vacuum at 80° C. for 5 h and at 200° C. for 2 h.

The yield, at a purity of >99.0% by HPLC, was 3.24-3.45 g, correspondingto 40.3-42.8%.

¹H NMR (CDCl₃): [ppm]=8.96 (m, 3H), 8.19 (m, 3H), 7.73 (m, 3H), 7.63 (m,6H), 7.15 (d, 3H), 7.10 (d, 3H), 6.97 (m, 6H), 6.86 (m, 3H).

Example 4 (Inventive) fac-tris[2-(1-isoquinolinyl-κN)phenyl-κC]iridium(III)

Procedure analogous to Example 3, except that iridium(III)acetylacetonate was replaced by 4.84 g of Na[Ir(acac)₂Cl₂] (Ir content39.69%) (10.0 mmol).

The yield, at a purity of >99.8% by HPLC, was 7.08-7.38 g, correspondingto 87.9-91.7%.

¹H NMR (DMSO): [ppm]=see Example 3.

Example 5 (Comparative Example)fac-tris[2-(2-pyridinyl-κN)benzo[b]thien-3-yl-κC]iridium(III)

4.90 g (10.0 mmol) of iridium(III) acetylacetonate and 21.13 g (100mmol) of 2-benzothien-2-ylpyridine were added to 100 ml of degassedethylene glycol. The suspension was heated under reflux (oil bathtemperature 180° C.) with good stirring for 40 h. After cooling to roomtemperature, a mixture of 240 ml of ethanol and 60 ml of aqueous 1Nhydrochloric acid was poured with stirring into the reaction mixturewhich contained thefac-tris[2-(2-pyridinyl-κN)benzo[b]thien-3-yl-κC]iridium(III) product inthe form of a red-brown, finely crystalline precipitate. After stirringfor 5 minutes, the crystals were filtered off through a glass suctionfilter (P3); the red-brown, finely crystalline precipitate was washedthree times with 30 ml of a mixture of ethanol and aqueous 1Nhydrochloric acid (4:1, v:v), five times with 30 ml of a mixture ofethanol and water (1:1, v:v) and five times with 30 ml of ethanol, andsubsequently dried under high vacuum at 80° C. for 5 h and at 200° C.for 2 h.

The yield, at a purity of >37.4% by HPLC, was 4.30-4.56 g, correspondingto 52.2-55.4%.

¹H NMR (CD₂Cl₂): [ppm]=7.73 (m, 3H), 7.53 (m, 6H) 7.35 (m, 3H), 7.05 (m,3H), 6.76 (m, 3H), 6.63 (m, 3H), 6.56 (m, 3H).

Example 6 (Inventive)fac-tris[2-(2-pyridinyl-κN)benzo[b]thien-3-yl-κC]iridium(III)

Procedure analogous to Example 3, except that iridium(III)acetylacetonate was replaced by 4.84 g of Na[Ir(acac)₂Cl₂] (Ir content39.69%) (10.0 mmol).

The yield, at a purity of >99.1% by HPLC, was 7.15-7.38 g, correspondingto 86.9-89.7%.

¹H NMR (CD₂Cl₂): [ppm]=see Example 5.

1. A process for preparing homoleptic Ir(III) complexes of the formula(I)

in which: CyD is a cyclic group which contains at least one donor atomvia which the cyclic group is bonded to the metal and which may in turnbear one or more substituents R; the CyD and CyC groups are joinedtogether via a covalent bond; CyC is a cyclic group which contains acarbon atom via which the cyclic group is bonded to the metal and whichmay in turn bear one or more substituents R; R is the same or differentat each instance and is H, F, Cl, Br, I, NO₂, CN, a straight-chain orbranched or cyclic alkyl or alkoxy group having from 1 to 20 carbonatoms, in which one or more nonadjacent CH₂ groups may be replaced by—O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which oneor more hydrogen atoms may be replaced by F, or an aryl or heteroarylgroup which has from 4 to 14 carbon atoms and may be substituted by oneor more nonaromatic R radicals; where a plurality of substituents R,both on the same ring and on the two different rings, together may inturn form a further mono- or polycyclic, aliphatic or aromatic ringsystem; R¹ and R² are the same or different at each instance and are Hor an aliphatic or aromatic hydrocarbon radical having from 1 to 20carbon atoms, characterized by the reaction of aniridium(III)-containing reactant which contains at least one diketonatestructural unit of the formula (II)

in which: R⁴, R⁶ are the same or different at each instance and are alinear, branched or cyclic alkyl group having 1-20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F or aromatic groups each having from3 to 14 carbon atoms, or an aryl and/or heteroaryl group having 3-20carbon atoms or an alkoxy group OR¹, R⁵ is the same or different at eachinstance and is a linear, branched or cyclic alkyl group having 1-20carbon atoms, in which one or more nonadjacent CH₂ groups may bereplaced by —O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and inwhich one or more hydrogen atoms may be replaced by F or aromatic groupseach having from 3 to 14 carbon atoms, or an aryl and/or heteroarylgroup having 3-20 carbon atoms, R¹ and R² are the same or different ateach instance and are H or an aliphatic or aromatic hydrocarbon radicalhaving from 1 to 20 carbon atoms, excluding homoleptic diketonatecomplexes of the formula (II) and compounds of the formula (II) whichcontain two ligands of the formula (III)

where the symbols CyC and CyD in formula (III) are each as defined underformula (I), with a compound of the formula (IV)

in which the symbols CyD and CyC are each as defined under formula (I).2. The process as claimed in claim 1, characterized in that theiridium(III)-containing reactant contains a structure of the formula (V)

where the symbols R⁴, R⁵ and R⁶ are each as defined in claim 1, X is thesame or different at each instance and is a monovalent anion, Y is thesame or different at each instance and is an uncharged monodentateligand, n is 0, 1 or 2 and m is 1− when n=2, is 0 when n=1 or is 1+ whenn=0.
 3. The process as claimed in claim 1, characterized in that theiridium(III)-containing reactant contains a structure of the formula(VI)

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z².
 4. The process as claimed in claim1, characterized in that the iridium(III)-containing reactant contains astructure of the formula (VII)

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, Z is the same or different at eachinstance and is and uncharged bidentate and/or bridging ligand Z⁰, amonoanionic bidentate and/or bridging ligand Z¹ or a dianionic bidentateand/or bridging ligand Z², n and p are the same or different at eachinstance and are 0 or 1, o can assume integer values from 0 to 100 000and m may be from (o+2)+ to (o+2)−.
 5. The process as claimed in claim1, characterized in that the iridium(III)-containing reactant contains astructure of the formula (VIII)

where the symbols and indices R⁴, R⁵ and R⁶ are each as defined in claim1, and in which G is the same or different at each instance and iseither a monovalent anion X or an uncharged monodentate ligand Y Z isthe same or different at each instance and is and uncharged bidentateand/or bridging ligand Z⁰, a monoanionic bidentate and/or bridgingligand Z¹ or a dianionic bidentate and/or bridging ligand Z², n and pare the same or different at each instance and are 0 or 1, and m is 2+,1+, 0, 1− or 2−.
 6. The process as claimed in claim 1, characterized inthat the iridium(III)-containing reactant contains a structure of theformula (IX)

where the symbols R¹, R², R⁴, R⁵ and R⁶ are each as defined in claim 1and in which Z is the same or different at each instance and is anduncharged bidentate and/or bridging ligand Z⁰, a monoanionic bidentateand/or bridging ligand Z¹ or a dianionic bidentate and/or bridgingligand Z² and m is 2+, 1+, 0, 1− or 2−.
 7. The process as claimed inclaim 1, characterized in that the iridium(III)-containing reactantcontains a structure of the formula (X)

where the symbols R⁴, R⁵ and R⁶ are each as defined in claim 1 and whereQ is the same or different at each instance and is a monovalent anion.8. The process as claimed in claim 1, characterized in that theiridium(III)-containing reactant contains a compound of the formula (V),(VII) and/or (VIII)

wherein R⁴ and R⁶ are the same or different at each instance and are alinear, branched or cyclic alkyl group having 1-20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F or aromatic groups each having from3 to 14 carbon atoms, or an aryl and/or heteroaryl group having 3-20carbon atoms or an alkoxy group OR¹, R⁵ is the same or different at eachinstance and is a linear, branched or cyclic alkyl group having 1-20carbon atoms, in which one or more nonadjacent CH₂ groups may bereplaced by —O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR═CR¹— or —C≡C—, and inwhich one or more hydrogen atoms may be replaced by F or aromatic groupseach having from 3 to 14 carbon atoms, or an aryl and/or heteroarylgroup having 3-20 carbon atoms, Y is the same or different at eachinstance and is an uncharged monodentate ligand, n is 0, 1 or 2 and m is1− when n=2, is 0 when n=1 or is 1+ when n=0,

where R⁴, R⁵ and R⁶ are each as defined above, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, Z is the same or different at eachinstance and is and uncharged bidentate and/or bridging ligand Z⁰, amonoanionic bidentate and/or bridging ligand Z¹ or a dianionic bidentateand/or bridging ligand Z², n and p are the same or different at eachinstance and are 0 or 1, o can assume integer values from 0 to 100 000and m may be from (o+2)+ to (o+2)−,

where the symbols and indices R⁴, R⁵ R⁶, G, Z, n and p are each asdefined above and in which m is 2+, 1+, 0, 1− or 2− and X is the same ordifferent at each instance and is OH⁻, F⁻, Cl⁻, Br⁻, I⁻, SCN⁻, CN⁻, SH⁻,SeH⁻, an alkoxide of the formula R¹O⁻, nitrate, a carboxylate of theformula R¹COO⁻, cyclopentadienide (C₅H₅ ⁻) or hydride (H⁻).
 9. Theprocess as claimed in claim 1, characterized in that theiridium(III)-containing reactant contains a compound of the formula (V),(VII) and/or (VIII)

wherein R⁴ and R⁶ are the same or different at each instance and are alinear, branched or cyclic alkyl group having 1-20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F or aromatic groups each having from3 to 14 carbon atoms, or an aryl and/or heteroaryl group having 3-20carbon atoms or an alkoxy group OR¹, R⁵ is the same or different at eachinstance and is a linear, branched or cyclic alkyl group having 1-20carbon atoms, in which one or more nonadjacent CH₂ groups may bereplaced by —O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and inwhich one or more hydrogen atoms may be replaced by F or aromatic groupseach having from 3 to 14 carbon atoms, or an aryl and/or heteroarylgroup having 3-20 carbon atoms, n is 0, 1 or 2 and m is 1− when n=2, is0 when n=1 or is 1+ when n=0

where R⁴, R⁵ and R⁶ are each as defined above, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, Z is the same or different at eachinstance and is and uncharged bidentate and/or bridging ligand Z⁰, amonoanionic bidentate and/or bridging ligand Z¹ or a dianionic bidentateand/or bridging ligand Z², n and p are the same or different at eachinstance and are 0 or 1, o can assume integer values from 0 to 100 000and m may be from (o+2)+ to (o+2)−,

where the symbols and indices R⁴, R⁵ R⁶, G, Z, n and p are each asdefined above and in which m is 2+, 0, 1− or 2−, and Y is the same ordifferent at each instance and is H₂O, H₂S, a dialkyl sulfide of theformula (R¹)₂S, a thiol of the formula R¹SH, an alcohol of the formulaR¹OH, an ether of the formula (R¹)₂O, a dialkyl sulfoxide (R¹)₂SO, NH₃,a primary, secondary or tertiary amine, pyridine, quinoline, a nitrileof the formula R¹CN, CO, a phosphine of the formula P(R¹)₃, a phosphineoxide of the formula OP(R¹)₃, an arsine of the formula As(R¹)₃ or aphosphite of the formula P(OR¹)₃.
 10. The process as claimed in claim 1,characterized in that the iridium(III)-containing reactant is a compoundof the formula (VI), (VII), (VIII) and/or (IX)

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z²,

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, n and p are the same or different ateach instance and are 0 or 1 o can assume integer values from 0 to 100000 and m may be from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above, m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2− and Z⁰ is the same or differentat each instance and is bipyridine, phenanthroline, ethylenediamine,propylenediamine, or 2-, 3- or 4-aminopyridine.
 11. The process asclaimed in claim 1, characterized in that the iridium(III)-containingreactant is a compound of the formula (VI), (VII), (VIII) and/or (IX)and

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z²,

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, n and p are the same or different ateach instance and are 0 or 1, o can assume integer values from 0 to 100000 and m may be from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above, m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2−, Z¹ is the same or different ateach instance and is diketonate, carboxylate, picolinate,aminocarboxylate, 1-ketoalkoxides, azide, cyanate, isocyanate,thiocyanate, isothiocyanate, chloride, bromide and iodide.
 12. Theprocess as claimed in claim 1, characterized in that theiridium(III)-containing reactant is a compound of the formula (VI),(VII), (VIII) and/or (IX) and

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z²,

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, n and p are the same or different ateach instance and are 0 or 1, o can assume integer values from 0 to 100000 and m may be from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above, m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2−, Z¹ is the same or different ateach instance and is acetylacetonate or acetate.
 13. The process asclaimed in claim 1, characterized in that the iridium(III)-containingreactant is a compound of the formula (VI), (VII), (VIII) and/or (IX)

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z²,

R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same or differentat each instance and is either a monovalent anion X or an unchargedmonodentate ligand Y, n and p are the same or different at each instanceand are 0 or 1, o can assume integer values from 0 to 100 000 and m maybe from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above, m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2−, and Z² is the same or differentat each instance and is oxalate, malonate, phthalate, isophthalate,terephthalate, oxide or peroxide.
 14. The process as claimed in claim 7,characterized in that the iridium(III)-containing reactant is a compoundof the formula (X) in which Q is Cl, Br, I or a diketonate.
 15. Theprocess as claimed in claim 1 claim 2, characterized in that theiridium(III)-containing reactant is a compound of the formula (V) inwhich X is the same or different at each instance and is a Cl, Br or Ianion.
 16. The process as claimed in claim 1, characterized in that theiridium(III)-containing reactant contains a compound of the formula (XI)

where R¹, R², R⁴, R⁵ and R⁶ are each as defined in claim 1, X is thesame or different at each instance and is a Cl, Br or I anion, and E isan alkali metal cation, ammonium or phosphonium ion.
 17. The process asclaimed in claim 1, characterized in that the iridium(III)-containingreactant used contains a mixture of at least 2 iridium(III)-containingreactants of the formula (II), or (V) to (XI)

wherein R⁴ and R⁶ are the same or different at each instance and are alinear, branched or cyclic alkyl group having 1-20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F or aromatic groups each having from3 to 14 carbon atoms, or an aryl and/or heteroaryl group having 3-20carbon atoms or an alkoxy group OR¹, R⁵ is the same or different at eachinstance and is a linear, branched or cyclic alkyl group having 1-20carbon atoms, in which one or more nonadjacent CH₂ groups may bereplaced by —O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and inwhich one or more hydrogen atoms may be replaced by F or aromatic groupseach having from 3 to 14 carbon atoms, or an aryl and/or heteroarylgroup having 3-20 carbon atoms. Y is the same or different at eachinstance and is an uncharged monodentate ligand, n is 0, 1 or 2 and m is1− when n=2, is 0 when n=1 or is 1+ when n=0

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging, ligand Z¹or a dianionic bidentate and/or bridging ligand Z², and m is 1+ whenZ=Z⁰, is 0 when Z=Z¹ and is 1− when Z=Z²,

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, n and p are the same or different ateach instance and are 0 or 1, o can assume integer values from 0 to 100000 and m may be from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2−, and

where the symbols R⁴, R⁵ and R⁶ are each as defined in claim 1 and whereQ is the same or different at each instance and is a monovalent anion

where R¹, R², R⁴, R⁵ and R⁶ are each as defined in claim 1, X is thesame or different at each instance and is a Cl, Br or I anion, and E isan alkali metal cation, ammonium or phosphonium ion.
 18. The process asclaimed in claim 1, characterized in that the reactant used is a mixturewhich comprises at least one iridium(III)-containing reactant of theformula (II), or (V) to (XI)

wherein R⁴ and R⁶ are the same or different at each instance and are alinear, branched or cyclic alkyl group having 1-20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F or aromatic groups each having from3 to 14 carbon atoms, or an aryl and/or heteroaryl group having 3-20carbon atoms or an alkoxy group OR¹, R⁵ is the same or different at eachinstance and is a linear, branched or cyclic alkyl group having 1-20carbon atoms, in which one or more nonadjacent CH₂ groups may bereplaced by —O—, —S—, —NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and inwhich one or more hydrogen atoms may be replaced by F or aromatic groupseach having from 3 to 14 carbon atoms, or an aryl and/or heteroarylgroup having 3-20 carbon atoms, Y is the same or different at eachinstance and is an uncharged monodentate ligand, n is 0, 1 or 2 and m is1− when n=2, is 0 when n=1 or is 1+ when n=0

where R⁴, R⁵ and R⁶ are each as defined in claim 1 and where Z is thesame or different at each instance and is and uncharged bidentate and/orbridging ligand Z⁰, a monoanionic bidentate and/or bridging ligand Z¹ ora dianionic bidentate and/or bridging ligand Z², and m is 1+ when Z=Z⁰,is 0 when Z=Z¹ and is 1− when Z=Z²,

where R⁴, R⁵ and R⁶ are each as defined in claim 1, G is the same ordifferent at each instance and is either a monovalent anion X or anuncharged monodentate ligand Y, n and p are the same or different ateach instance and are 0 or 1, o can assume integer values from 0 to 100000 and m may be from (o+2)+ to (o+2)−

where the symbols and indices R⁴, R⁵ and R⁶, G, Z, n and p are each asdefined above, m is 2+, 1+, 0, 1− or 2−

where the symbols R¹, R², R⁴, R⁵, R⁶ and Z are each as defined in claim1 and in which m is 2+, 1+, 0, 1− or 2−, and

where the symbols R⁴, R⁵ and R⁶ are each as defined in claim 1 and whereQ is the same or different at each instance and is a monovalent anion

where R¹, R², R⁴, R⁵ and R⁶ are each as defined in claim
 1. X is thesame or different at each instance and is a Cl, Br or I anion, and E isan alkali metal cation, ammonium or phosphonium ion.
 19. HomolepticIr(III) complexes of the formula (I) formula (I)

in which: CyD is a cyclic group which contains at least one donor atomvia which the cyclic group is bonded to the metal and which may in turnbear one or more substituents R; the CyD and CyC groups are joinedtogether via a covalent bond; CyC is a cyclic group which contains acarbon via which the cyclic group is bonded to the metal and which mayin turn bear one or more substituents R; R is the same or different ateach instance and is H, F, Cl, Br, NO₂, CN, a straight-chain or branchedor cyclic alkyl or alkoxy group having from 1 to 20 carbon atoms, inwhich one or more nonadjacent CH₂ groups may be replaced by —O—, —S—,—NR¹—, —CONR²—, —CO—O—, —CR¹═CR¹— or —C≡C—, and in which one or morehydrogen atoms may be replaced by F, or an aryl or heteroaryl groupwhich has from 4 to 14 carbon atoms and may be substituted by one ormore nonaromatic R radicals; where a plurality of substituents R, bothon the same ring and on the two different rings, together may in turnform a further mono- or polycyclic, aliphatic or aromatic ring system;R¹ and R² are the same or different at each instance and are H or analiphatic or aromatic hydrocarbon radical having from 1 to 20 carbonatoms, characterized in that they have been obtained by a process asclaimed in claim
 1. 20. Homoleptic Ir(III) complexes as claimed in claim19, characterized in that their purity is >99%.